Apparatus and method for determining d2d data resource for d2d communication

ABSTRACT

A method and apparatus for supporting a device-to-device (D2D) communication between user equipments (UEs) are provided. The method includes: receiving, at a UE, configuration information associated with a D2D data transmission resource, the configuration information including information of a D2D data allocation period and being transmitted from an evolved NodeB (eNB); determining, at the UE, a D2D data transmission resource offset and a period associated with a D2D data transmission resource bitmap in each D2D data allocation period, the D2D data transmission resource bitmap including at least one bit corresponding to bit value “1”; and determining a pool of subframes corresponding to the bit value “1” of the D2D data transmission resource bitmap, the period associated with the D2D data transmission resource bitmap including the pool of subframes, the pool of subframes corresponding to D2D data transmission resources through which a D2D data transmission is capable.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/657,030, filed on Jul. 21, 2017, which is a continuation of U.S.patent application Ser. No. 14/819,232, flied on Aug. 5, 2015, nowissued as U.S. Pat. No. 9,750,016, which claims priority from and thebenefit of Korean Patent Application No. 10-2014-0102572, filed on Aug.8, 2014, each of which is hereby incorporated by reference in itsentirety.

BACKGROUND 1. Field

The present disclosure relates to wireless communication, and moreparticularly, to a method and apparatus for determining D2D dataresources for Device to Device (D2D) communication.

2. Discussion of the Background

An amount of data transmitted through wireless communication hasgradually increased. However, the frequency resources that serviceproviders can provide are limited and have become increasinglysaturated, and thus, mobile carriers continuously develop technologiesfor discovering new frequencies and improving efficient use offrequencies. One of the actively studied technologies to ease thefrequency resource shortage and to create a new mobile communicationservice is Device-to-Device (D2D) communication technology.

D2D communication refers to a technology in which User Equipments (UEs)which are geometrically adjacent to one another, directly transmit andreceive information without passing through an infrastructure, such as abase station. In the initial stage, the D2D communication technology wasdeveloped and standardized mostly in a non-licensed band such as Wi-Fi,Direct, Bluetooth, which have been already commercialized. However,recently, the development of technologies and standardization forsupporting D2D communication in a cellular system that uses a licensedband, are underway. Representatively, the 3^(rd) Generation PartnershipProject (3GPP), which is a mobile communication standardizationassociation, actively conducts D2D communication technologystandardization that is referred to as Proximity-based services (ProSe),which is one of the new technologies included in Long Term Evolution(LTE).

However, for the LTE wireless communication system, a method for usingdata resources for effectively providing D2D services has not beendetermined. Therefore, there is desire for a method of using resourcesfor effectively supporting services.

SUMMARY

The present disclosure relates to a method and apparatus for determininga D2D data resource for a D2D data transmission.

An exemplary embodiment provides a method of determining adevice-to-device (D2D) data transmission resource for a user equipment(UE), the method including: receiving, at a UE, configurationinformation associated with a D2D data transmission resource, theconfiguration information including information of a D2D data allocationperiod and being transmitted from an evolved NodeB (eNB); determining,at the UE, a D2D data transmission resource offset and a periodassociated with a D2D data transmission resource bitmap in each D2D dataallocation period, the D2D data transmission resource bitmap includingat least one bit corresponding to bit value “1”; and determining a poolof subframes corresponding to the bit value “1” of the D2D datatransmission resource bitmap, the period associated with the D2D datatransmission resource bitmap including the pool of subframes, the poolof subframes corresponding to D2D data transmission resources throughwhich a D2D data transmission is capable.

An exemplary embodiment provides a user equipment (UE) to determine adevice-to-device (D2D) data transmission resource including: a wirelesstransceiver configured to: receive configuration information associatedwith a D2D data transmission resource, the configuration informationincluding information of a D2D data allocation period and beingtransmitted from an evolved NodeB (eNB); and one or more processorsconfigured to: determine a D2D data transmission resource offset and aperiod associated with a D2D data transmission resource bitmap in eachD2D data allocation period, the D2D data transmission resource bitmapincluding at least one bit corresponding to bit value “1”; and determinea pool of subframes corresponding to the bit value “1” of the D2D datatransmission resource bitmap, the period associated with the D2D datatransmission resource bitmap including the pool of subframes, the poolof subframes corresponding to D2D data transmission resources throughwhich a D2D data transmission is capable.

An exemplary embodiment provides a method of determining adevice-to-device (D2D) data transmission resource for a user equipment(UE), the method including: receiving, at a UE, configurationinformation associated with a D2D data transmission resource, theconfiguration information including information of a D2D data allocationperiod, information of a D2D data transmission resource offset, andinformation of a D2D data transmission resource bitmap; determining, atthe UE, a D2D data transmission resource in the D2D data allocationperiod among uplink subframes configured based on a radio framestructure of a Frequency Division Duplexing (FDD) scheme or a TimeDivision Duplexing (TDD) scheme, each radio frame according to the radioframe structure including 10 subframes. The determining of the D2D datatransmission resource includes: determining, within the D2D dataallocation period, a plurality of repetitions of a D2D data transmissionresource bitmap based on the D2D data transmission resource offset.

A collision or interference between User Equipments (UEs) caused bytransmission and/or reception of Device-to-Device (D2D) data may bereduced or minimized based on assignment of D2D data resources used forD2D communication. Therefore, the performance of the D2D datatransmission may be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram illustrating a structure of a radio frameaccording to an exemplary embodiment.

FIG. 2 is a conceptual diagram illustrating a structure of a radio frameaccording to an exemplary embodiment.

FIG. 3 is a conceptual diagram illustrating D2D communication accordingto an exemplary embodiment.

FIG. 4 is a conceptual diagram illustrating a resource allocation unit,defined in D2D communication according to an exemplary embodiment.

FIG. 5 is a conceptual diagram illustrating a method of allocating a D2Ddata transmission resource, to a User Equipment (UE) or a UE group,according to an exemplary embodiment.

FIG. 6 is a conceptual diagram illustrating a method of allocating a D2Ddata transmission resource, to a UE or a UE group, according to anexemplary embodiment.

FIG. 7 is a conceptual diagram illustrating a method of transmittinginformation for D2D communication according to an exemplary embodiment.

FIG. 8 is a conceptual diagram illustrating a method of transmittinginformation for D2D communication according to an exemplary embodiment.

FIG. 9 is a conceptual diagram illustrating operations of a first UE anda second UE in FDD, according to an exemplary embodiment.

FIG. 10 is a conceptual diagram illustrating operations of a first UEand a second UE in TDD, according to an exemplary embodiment.

FIG. 11 is a flowchart illustrating a traffic data transmissionoperation of a UE according to an exemplary embodiment.

FIG. 12 is a flowchart illustrating a traffic data reception operationof a UE according to an exemplary embodiment.

FIG. 13 is a block diagram illustrating a Base Station (BS) and a UEaccording to an exemplary embodiment.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Exemplary embodiments will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof inventive concept are shown. Throughout the drawings and the detaileddescription, unless otherwise described, the same drawing referencenumerals are understood to refer to the same elements, features, andstructures. In describing the exemplary embodiments, detaileddescription on known configurations or functions may be omitted forclarity and conciseness.

Further, the terms, such as first, second, A, B, (a), (b), and the likemay be used herein to describe elements in the description herein. Theterms are used to distinguish one element from another element. Thus,the terms do not limit the element, an arrangement order, a sequence orthe like. It will be understood that when an element is referred to asbeing “on”, “connected to” or “coupled to” another element, it can bedirectly on, connected or coupled to the other element or interveningelements may be present. The present specification provides descriptionsin association with a wireless communication network, and tasks executedin the wireless communication network may be performed in the processwhere a system (for example, a base station) that manages thecorresponding wireless communication network controls the network andtransmits data, or may be performed in a User Equipment (UE) that iswireless linked to the corresponding network and capable ofcommunicating with the network system.

FIG. 1 is a conceptual diagram illustrating a structure of a radio frameaccording to an exemplary embodiment.

FIG. 1 illustrates a structure of a radio frame for Frequency DivisionDuplexing (FDD)-based Device-to-Device (D2D) communication.

Referring to FIG. 1, a radio frame may include ten subframes. A singlesubframe includes two slots. A time (a length) in which a singlesubframe is transmitted is referred to as a Transmission Time Interval(TTI). Referring to FIG. 2, for example, a length of a single subframe(1 subframe) may be 1 ms, and a length of a single slot (1 slot) may be0.5 ms.

A single slot may include a plurality of symbols in a time domain. Forexample, in a wireless system that uses Orthogonal Frequency DivisionMultiple Access (OFDMA) in a Downlink (DL), the symbol may be anOrthogonal Frequency Division Multiplexing (OFDM) symbol and in awireless system that uses Single Carrier-Frequency Division MultipleAccess (SC-FDMA) in an Uplink (UL), the symbol may be an SC-FDMA symbol.An expression associated with a symbol period of the time domain may notbe limited by a multiple access scheme or name.

The number of symbols included in a single slot may be different basedon a length of a Cyclic Prefix (CP). For example, in the case of anormal CP, seven symbols are included in a single slot, and in the caseof an extended CP, six symbols are included in a single slot.

For FDD, when two component carrier frequencies exist, the two componentcarrier frequencies may be used for uplink transmission and downlinktransmission, respectively. Hereinafter, from the perspective of asingle D2D User Equipment (UE) (hereinafter referred to as a UE) thatsupports predetermined D2D communication, uplink transmission refers todata transmission from the UE to another UE or to a Base Station (BS),and uplink data refers to data transmitted from the UE to the other UEor the BS. Also, from the perspective of the UE, downlink transmissionrefers to data transmission from another UE or a BS to the UE, anddownlink data refers to data transmitted from the other UE or the BS tothe UE.

For duplexing scheme-based FDD, downlink transmission and uplinktransmission may be executed in a cell, in parallel. Although uplinktransmission and downlink transmission are parallelly executable in asingle cell in FDD, downlink transmission and uplink transmission maynot be executed in parallel, depending on whether a UE supports fullduplex or half duplex. For example, when a UE operates as a full-duplexmode, the UE may receive downlink data and may transmit uplink data, inparallel. However, when the UE operates as a half-duplex mode, the UEmay not simultaneously execute reception of downlink data andtransmission of uplink data.

In D2D communication, when a UE operates as a full-duplex mode, the UEmay receive downlink data from another UE or a BS, and may transmituplink data to another UE or the BS, in parallel. However, when the UEoperates as a half-duplex mode, the UE may not parallelly executereception of downlink data from another UE or a BS, and transmission ofuplink data to another UE or the BS.

FIG. 2 is a conceptual diagram illustrating a structure of a radio frameaccording to an exemplary embodiment.

FIG. 2 illustrates a structure of a radio frame for Time DivisionDuplexing (FDD)-based D2D communication.

Referring to FIG. 2, a radio frame structure for the TDD may include 10subframes, like the radio frame structure of the FDD. A single subframeincludes two slots. Basically, the radio frame structures are similar.However, a predetermined subframe among subframes included in the radioframes of the TDD may be defined as a special subframe. The specialsubframe may be a time resource for switching uplink transmission anddownlink reception. The special subframe may be formed of a downlinkpart (DwPTS), a Guard Period (GP), and an uplink part (UpPTS).

In TDD, only a single carrier frequency exists, and thus, uplinktransmission and downlink transmission may be distinguished based ontime in a single cell. For example, on a single carrier frequency, a UEthat executes D2D communication, transmits uplink data to another UE ora BS in a time resource for uplink transmission and receives downlinkdata from another UE or the BS in a time resource for downlinktransmission.

FIG. 3 is a conceptual diagram illustrating D2D communication.

D2D communication refers to a technology in which UEs directly receiveand transmit data. Hereinafter, a UE disclosed in exemplary embodimentsis assumed to support D2D communication.

When UEs located close to one another execute D2D communication in acellular system, loads on an evolved NodeB (eNodeB) may be dispersed. Inaddition, when UEs execute D2D communication, a UE transmits data arelatively short distance, and thus, transmission power consumption andtransmission latency of the UE may decrease. In addition, from theperspective of the whole system, the existing cellular-basedcommunication and the D2D communication use identical resources, andthus, frequency utilization efficiency may be improved.

The D2D communication may be classified into a communication method of aUE located within a network coverage (base station coverage) and acommunication method of a UE located outside a network coverage (basestation coverage).

Referring to FIG. 3, the communication between a first UE 310 located ina first cell and a second UE 320 located in a second cell may be D2Dcommunication between a UE included in a network coverage and a UEincluded in a network coverage. The communication between a fourth UE340 located in the first cluster and a fifth UE 350 located in the firstcluster may be D2D communication between the UEs located outside anetwork coverage. The fifth UE 350 is the cluster header, and thecluster header may operate as an independent Synchronization Source(ISS) for synchronization of an out-of coverage UE.

The D2D communication may include a discovery process that executesdiscovery for communication between UEs and a direct communicationprocess in which UEs transmit and receive control data and/or trafficdata.

The D2D communication may be used for various purposes. For example, D2Dcommunication within a network coverage and D2D communication outside anetwork coverage may be used for public safety. The D2D communicationoutside a network coverage may be used for only the public safety. D2Dcommunication in a BS coverage may be executed based on a BS. Forexample, a BS 300 may transmit D2D resource allocation information tothe first UE 310 located in the BS coverage. The D2D resource allocationinformation may include allocation information associated with a D2Dcommunication resource for D2D communication between the first UE 310and another UE (for example, a second UE 320). The first UE 310 thatreceives the D2D resource allocation information from the BS, maytransmit the D2D resource allocation information to the second UE 320outside the BS coverage. The second UE 320 may be a UE located outsidethe BS coverage, from the perspective of the BS 300 of a first cell. Thefirst UE 310 and the second UE 320 may execute D2D communication basedon the D2D resource allocation information. Particularly, the second UE320 may obtain information associated with the D2D communicationresource of the first UE 310. The second UE 320 may receive traffic dataand/or control data transmitted from the first UE 310, through aresource indicated by the information associated with the D2Dcommunication resource of the first UE 310.

In the D2D communication, a UE may transmit control data to another UE.A separate channel (for example, a Physical Uplink Control Channel(PUCCH)) for transmitting control data may not be defined in the D2Dcommunication. When the control channel is not defined in the D2Dcommunication, a UE may use various methods for transmitting controldata for D2D communication. In the D2D communication, the control datamay be expressed as Scheduling Assignment (SA) information. In the D2Dcommunication, actual traffic data (e.g., data transmitted throughshared channel, such as physical sidelink shared channel) distinguishedfrom control data, may be expressed as D2D data.

The D2D communication within network coverage may be expressed as firstmode communication, and the D2D communication outside network coveragemay be expressed as second mode communication. In the first modecommunication, a BS or a relay node schedules accurate informationassociated with resources for the D2D communication between UEs.Particularly, according to the first mode communication, a BS transmits,to a UE, resource allocation information associated with control data(or SA data) and resource allocation information associated with trafficdata (or D2D data).

According to the second mode communication, a UE may directly scheduleresources for D2D communication, based on a D2D resource pool.Particularly, in the second mode communication, resource allocationinformation for transmission of control data and resource allocationinformation associated with traffic data may be selected by a UE fromthe D2D resource pool. The D2D resource pool may be pre-configured orsemi-statically allocated.

Within the network coverage, the first mode communication or the secondmode communication may be used as a D2D communication. Outside thenetwork coverage, the second mode communication may be used as a D2Dcommunication.

A D2D communication resource for transmitting or receiving control dataor traffic data for D2D communication, may roughly include a D2D SAresource for transmitting control data and a D2D data resource fortransmitting traffic data.

The D2D data resource may be a resource used for transmitting and/orreceiving traffic data in D2D communication.

The D2D data resource may be defined based on a subframe unit in a timeaxis and based on a Resource Block (RB) unit in a frequency axis, butthis may not be limited thereto. The D2D data resource may be acandidate resource that may transmit traffic data by a D2D UE. That is,the D2D data resource may be expressed as a D2D data candidate resourceor a D2D data transmission opportunity. A UE may transmit traffic datathrough a part or the entirety of the D2D data resource. The D2D dataresource that is actually used by a UE for transmitting traffic data maybe expressed as a selected D2D data resource.

The D2D SA resource may be a resource that is used for transmittingand/or receiving control data in D2D communication. In the same manner,the D2D SA resource may be defined based on a subframe unit in a timeaxis and based on a Resource Block (RB) unit in a frequency axis, butthis may not be limited thereto. The D2D SA resource may be a candidateresource that may transmit control data by a D2D UE. That is, the D2D SAresource may be expressed as a D2D SA candidate resource or a D2D SAtransmission opportunity. The UE may transmit control data through apart of the D2D SA resource. The D2D SA resource that the UE actuallyuses for transmitting control data, may be expressed as a selected D2DSA resource.

A selected D2D data resource and a selected D2D SA resource may bedefined, respectively, by patterns on the D2D data resource and the D2DSA resource. The pattern associated with the selected D2D data resourceand/or the pattern associated with the selected D2D SA resource may beexpressed as a Resource Pattern for Transmission (RPT), andparticularly, may be expressed as a Time Resource Pattern forTransmission (T-RPT) on the time axis.

A set of D2D data resources may be expressed as a D2D data resourcepool, and a set of D2D SA resources may be expressed as a D2D SAresource pool. The D2D resource pool may be used as a concept includingthe D2D data resource pool and the D2D SA resource pool.

Hereinafter, an exemplary embodiment will disclose a method of defininga D2D data resource in a D2D data allocation period, in detail.Hereinafter, a D2D data resource may be classified into a D2D datatransmission resource used for D2D data transmission and a D2D datareception resource used for D2D data reception.

FIG. 4 is a conceptual diagram illustrating a resource allocation unit,defined in D2D communication according to an exemplary embodiment.

FIG. 4 discloses a D2D data transmission resource defined in a D2D dataallocation period.

Referring to FIG. 4, a D2D data allocation period 400 may be apredetermined time unit for allocating D2D data transmission resources.The D2D data allocation period 400 may be a single value defined inadvance, or may be a value selected from among a plurality of D2D dataallocation period values defined in advance. For example, a D2D dataallocation period may be 40 ms, 80 ms, 160 ms, or 320 ms When the D2Ddata allocation period 400 is executed in subframes, the D2D dataallocation period may be 40, 80, 160, or 320 subframe units.

A D2D data transmission resource (or a transmission opportunity) may bedefined based on at least one subframe unit within the D2D dataallocation period 400. The D2D data transmission resource defined basedon at least one subframe unit may be expressed using a term called aunit D2D data transmission resource 420. That is, the D2D datatransmission resource defined in the D2D allocation period may be a setof at least one unit D2D data transmission resource 420. The unit D2Ddata transmission resource 420 may be defined based on a single subframeunit, as illustrated in FIG. 4, and may be defined based on a pluralityof subframe units. Hereinafter, descriptions will be provided under anassumption of the case in which the unit D2D data transmission resource420 is configured based on a single subframe.

A single D2D data transmission unit may be transmitted on the unit D2Ddata transmission resource 420. The D2D data transmission unit may be aMAC Protocol Data Unit (PDU) in a MAC layer or a data Transport Block(TB) in a physical layer.

According to an exemplary embodiment, the D2D data transmission resource420 may be allocated by taking into consideration a D2D datatransmission resource offset 440 in the D2D data allocation period 400,a D2D data transmission resource bitmap 460, and the number ofrepetitions 480 of a D2D data resource indication bitmap.

The D2D data transmission resource offset 440 may indicate theallocation location of a first D2D data transmission resource bitmap inthe D2D data allocation period. The D2D data transmission resourceoffset 440 may be a time interval corresponding to N subframes on a timeaxis. The D2D data transmission resource offset 440 may indicate astarting point of a D2D data transmission resource that is based on aD2D data transmission resource bitmap. Particularly, on subframes aftera point indicated as the D2D data transmission resource offset 440, aD2D data transmission resource that is based on the D2D datatransmission resource bitmap 460 is repeated as many as the number ofrepetitions 480 of a D2D data transmission resource bitmap.

The D2D data transmission resource bitmap 460 may be defined on asubframe unit including B subframes, in time axis. The subframe unitthat defines the D2D data transmission resource bitmap 460 may beexpressed as a bitmap subframe unit.

Bits on the D2D data transmission resource bitmap 460 correspond tosubframes included in the bitmap subframe unit, respectively, and thenumber of subframes included in the bitmap subframe unit may be thelength of the D2D data transmission resource bitmap 460. For example,when the number of subframes included in the bitmap subframe unit is B,the length of the D2D data transmission resource bitmap 460 may be B.Although B may be a predetermined value determined by taking intoconsideration a D2D data resource allocation period among multiples of 8or multiples of 10, this may not be limited thereto, and various valuesmay be used. For example, when the length of a single radio frame is 10ms, the length of the D2D data transmission resource bitmap 460 isdefined as 10, or may be indicated as a form in which it is repeated inthe D2D data allocation period 400. Alternatively, the length of the D2Ddata transmission resource bitmap 460 may be defined as 5, or may beindicated as a form in which it is repeated in the D2D data allocationperiod 400. Alternatively, the length of the D2D data transmissionresource bitmap 460 may be defined as 20, or may be indicated as a formin which it is repeated in the D2D data allocation period 400.

When the D2D data transmission resource 420 corresponds to a pluralityof subframes, bits on the D2D data transmission resource bitmap 460 maycorrespond to unit D2D data transmission resources (plurality ofsubframes) included in the bitmap subframe unit, respectively.Hereinafter, an exemplary embodiment will provide descriptions under anassumption that bits of the D2D data transmission resource bitmap 460correspond to subframes included in a bitmap subframe unit,respectively.

Values of the plurality of bits included in the D2D data transmissionresource bitmap 460 may be 0 or 1. When a bit value corresponding to apredetermined subframe of the D2D data transmission resource bitmap 460is 1, the predetermined subframe may be a D2D data transmissionresource. When a bit value corresponding to a predetermined subframe ofthe D2D data transmission resource bitmap 460 is 0, the predeterminedsubframe may be a non-D2D data transmission resource. Conversely, when abit value corresponding to a predetermined subframe on the D2D datatransmission resource bitmap 460 is 0, the predetermined subframe may bea D2D data transmission resource, and when a bit value corresponding toa predetermined subframe on the bit map is 1, the predetermined subframemay be a non-D2D data transmission resource.

In FIG. 4, the length B of the D2D data transmission resource bitmap 460is 10, and the D2D data transmission resource bitmap 460 may be‘1010010100.’ The bits of the bitmap may sequentially correspond to 10subframes, respectively, from the most significant bit to the leastsignificant bit. That is, the length of the D2D data transmissionresource bitmap 460 may be 10, and the D2D data transmission resourcebitmap 460 may indicate, as a D2D data transmission resource, 4subframes that correspond to a bit value of 1, from among the 10subframes.

The number of repetitions 480 of a D2D data transmission resource bitmapmay be the number of repetitions of a bitmap subframe unit. When thelength of the D2D data transmission resource bitmap 460 is B, the numberof repetitions R of a bitmap subframe unit on a time axis may bedetermined as 0<R≤└(P−C)/B┘. Here, P denotes a D2D data allocationperiod, and C denotes a D2D data transmission resource offset.

For example, as illustrated in FIG. 4, when the length B of the D2D datatransmission resource bitmap 460 is 10 ms, the D2D data resource offset440 is 2 ms, the D2D data resource allocation period 400 is 160 ms (or160 subframes), the number of repetitions R 480 of the D2D datatransmission resource bitmap may be a value in a range of 0<R≤15. Thatis, at most 15 repetitions may be executed. When the number ofrepetitions of the D2D data transmission resource bitmap is less than15, a D2D data transmission resource based on the D2D data transmissionresource bitmap 460 may be allocated within only a few subframes in theD2D data resource allocation period 400.

As the D2D data allocation period P 400 becomes long, and the D2D datatransmission resource offset C 440 and the length B of the D2D datatransmission resource bitmap 460 becomes short, the number ofrepetitions 480 of the D2D data transmission resource bitmap becomeshigh.

By taking into consideration the maximum value of the number ofrepetitions 480 of the D2D data transmission resource bitmap, a D2D datatransmission resource may be allocated in the D2D data allocation period400. For example, when P=320, C=0, and B=8, 0<R≤40. In this instance, asthe number of repetitions 480 of the D2D data transmission resourcebitmap, one out of 1 to 40 may be selected. Based on the selected valuecorresponding to the number of repetitions 480 of the D2D datatransmission resource bitmap, a D2D data transmission resource may beallocated in the D2D data allocation period 400.

Information associated with the D2D data allocation period 400,information associated with the D2D data transmission resource offset440, information associated with the D2D data transmission resourcebitmap 460, and information associated with the number of repetitions480 of the D2D data transmission resource bitmap may be commoninformation for UEs included in a UE set.

Information for allocating a D2D data transmission resource to anindividual UE or a UE group, may be UE-specific information of a UEgroup-specific information. The information for allocating the D2D datatransmission resource 420 to an individual UE or a UE group may beexpressed as a term called D2D data transmission resource allocationinformation. A method of allocating the D2D data transmission resource420 to an individual UE or a UE group based on UE-specific informationor UE group-specific information will be described based on the D2D datatransmission resource allocation information.

The UE set may be defined by various schemes. For example, in a firstmode communication (for example, D2D communication within a networkcoverage), a UE set may be a set of UEs that execute D2D communicationbased on information associated with the D2D data allocation period 400determined based on a BS, information associated with the D2D datatransmission resource offset 440, information associated with the D2Ddata transmission resource bitmap 460, information associated with thenumber of repetitions 480 of the D2D data transmission resource bitmap,and the D2D data transmission resource allocation information. The UEset of the first mode communication may include a UE in a BS coverage,and a UE that is outside the BS coverage and executes D2D communicationwith the UE in the BS coverage.

In a second mode communication (for example, D2D communication outside anetwork coverage (the second mode communication may be applicable in theD2D communication within the network coverage as described above)), a UEset may be a set of UEs that receive information associated with the D2Ddata allocation period 400 determined based on an ISS, informationassociated with the D2D data transmission resource offset 440,information associated with the D2D data transmission resource bitmap460, information associated with the number of repetitions 480 of theD2D data transmission resource bitmap, and the D2D data transmissionresource allocation information. For example, the UE set of the secondmode communication may include a UE within an IndependentSynchronization Source (ISS) coverage, and a UE that is outside the ISScoverage and executes D2D communication with the UE within the ISScoverage. Herein, the ISS may be a D2D synchronization source that isdifferent from an eNodeB from among D2D synchronization sources, andwhich do not transmit synchronization from other D2D synchronizationsources but transmit synchronization of itself, and may be a UE that isnot be scheduled by another source (a BS or another UE), is used as areference for operation synchronization of D2D communication, andschedules another UE.

Hereinafter, common information for UEs included in a UE set, such asinformation associated with the D2D data allocation period 400,information associated with the D2D data transmission resource offset440, information associated with the D2D data transmission resourcebitmap 460, and information associated with the number of repetitions480 of the D2D data transmission resource bitmap, may be expressed ascell-specific information. Also, like the D2D data transmission resourceallocation information, information for allocating a D2D datatransmission resource to an individual UE or a UE group, may beexpressed as UE group-specific information or UE-specific information.

FIG. 5 is a conceptual diagram illustrating a method of allocating a D2Ddata transmission resource, to a UE or a UE group, according to anexemplary embodiment.

FIG. 5 discloses a method of allocating a D2D data transmission resourceto a UE or a UE group. Hereinafter, for ease of description,descriptions will be provided from the perspective of a UE group, but aUE group may be a grouping unit including at least one UE, and may beconstrued as a single UE.

Referring to FIG. 5, the number of repetitions of a D2D datatransmission resource bitmap may be R. For ease of description, it isassumed that R times-repeated D2D data transmission resource bitmaps aresequentially indexed with B₀ through B_(R-1). D2D data transmissionsubframes corresponding to the R times-repeated D2D data transmissionresource bitmaps may be allocated to a UE group.

As illustrated in FIG. 5, when the number of UE groups is 2, xtimes-repeated D2D data transmission resource bitmaps (D2D datatransmission resource bitmaps indexed with B₀ to B_(x-1)) from among theR times-repeated D2D data transmission resource bitmaps, may indicate aD2D data transmission resource 500 for UE group 0. The remaining R-xtimes-repeated D2D data transmission resource bitmaps (D2D datatransmission resource bitmaps indexed with B_(x) to B_(R-1)) mayindicate a D2D data transmission resource 550 of UE group 1.

As another method, it is assumed that the number of repetitions of a D2Ddata transmission resource bitmap is R, and the number of UE groups isN. The number of repetitions of a D2D data transmission resource bitmapfor UE group 0 to UE group N−1, may be defined as r₀, r₁, r_(N-1), andr₀+r₁+ . . . +r_(N-1)=R. In this instance, the D2D data transmissionresource for UE group 0 may be determined based on r₀ times-repeated D2Ddata transmission resource bitmaps. Alternatively, the D2D datatransmission resource for UE group 1 may be determined based on r₁times-repeated D2D data transmission resource bitmaps, and a D2D datatransmission resource for UE group N−1 may be determined based onr_(N-1) times-repeated D2D data transmission resource bitmaps. Althoughthe D2D data transmission resources for UE group 0 to UE group N−1 maybe sequentially allocated in a D2D data allocation period, this may notbe limited thereto, and the D2D data transmission resources for UE group0 to UE group N−1 may be allocated based on various combinations in theD2D data allocation period.

A D2D data transmission subframe allocated to a UE group may bedetermined based on various methods.

The D2D data transmission subframe may be allocated to a UE group basedon a UE identifier.

A UE group may be grouped based on an identifier of a UE. A D2D datatransmission subframe allocated for each UE group may be indicated. Whenthe number of repetitions of a D2D data transmission resource bitmap isR, UEs are grouped by executing a modular arithmetic with respect to avalue corresponding to a UE identifier, and a D2D data transmissionsubframe allocated to the UE group may be determined. A UE identifiermay be UE group-specific information or UE-specific informationallocated to a UE through a D2D SA transmission resource.

The number of repetitions of a D2D data transmission resource bitmap forUE group 0 to UE group N−1, may be defined as r₀, r₁, . . . , r_(N-1),and r₀+r₁+ . . . +r_(N-1)=R. A UE that has a remainder of 0 obtainingafter executing a modular N arithmetic with respect to the value of a UEidentifier, is classified into UE group 0, and a UE that has a remainderof 1 obtaining after executing a modular N arithmetic with respect tothe value of a UE identifier, is classified into UE group 1. That is,when a UE that has a remainder of n obtaining after executing a modularN arithmetic may be classified into UE group n.

A UE included in UE group 0 may be allocated with a D2D datatransmission resource that is based on r₀ times-repeated D2D datatransmission resource bitmaps, a UE included in UE group 1 may beallocated with a D2D data transmission resource that is based on r₁times-repeated D2D data transmission resource bitmaps, and a UE includedin UE group n may be allocated with a D2D data transmission resourcethat is based on r_(n) times-repeated D2D data transmission resourcebitmaps.

r₀, r₁, . . . , and r_(N-1) may be defined in advance. For example, eachof r₀, r₁, . . . , and r_(N-2) may be └R/N┘ or ┌R/N┐, and r_(N-1) may beR−(r₀+r₁+ . . . +r_(N-2)).

For example, when R=15 and N=2, a modular 2 arithmetic may be executedwith respect to the value of a UE identifier. When a value obtainedafter executing the modular 2 arithmetic with respect to the value ofthe UE identifier is 0, a D2D data resource determined based on thenumber of repetitions of a D2D data transmission resource bitmapcorresponding to ┌R/N┐=8, may be allocated to a UE. When the valueobtained after executing the modular 2 arithmetic with respect to thevalue of the UE identifier is 1, a D2D data resource determined based onthe number of repetitions of a D2D data transmission resource bitmapcorresponding to R−┌R/N┐=7, may be allocated to the UE.

As another method, a D2D data transmission subframe may be allocated toa UE group, based on an RRC signaling.

A method of allocating a D2D data transmission resource to a UE groupthrough an RRC signaling will be described.

Information associated with a D2D data transmission subframe to be usedfrom among D2D data transmission subframes that are based on Rtimes-repeated D2D data transmission resource bitmaps, may betransmitted to a UE group, through an RRC signaling.

As described above, when the D2D data transmission resource bitmap isrepeated R times, the R times-repeated D2D data transmission resourcebitmaps may be indexed with B₀ to B_(R-1) Information indicating a UEgroup for which a D2D data transmission subframe based on each of theD2D data transmission resource bitmaps corresponding to B₀ to B_(R-1),is to be used, may be transmitted through an RRC signaling. For example,an upper bitmap for indicating D2D data transmission resource bitmapscorresponding to B₀ to B_(R-1) may be transmitted through an RRCsignaling. That is, R-bit bitmap may be a bitmap for indicating each ofthe D2D data transmission resource bitmaps corresponding to B₀ toB_(R-1). For example, when R is 5, ‘11000’ may indicate D2D datatransmission resource bitmaps corresponding to B₀ to B_(R-1). That is,when a bitmap for indicating each D2D data transmission resource bitmapfor a predetermined UE group is ‘11000’, the predetermined UE group maybe allocated with a D2D data transmission resource that is based on D2Ddata transmission resource bitmaps corresponding to B₀ to B₁.

As another method, a D2D data transmission subframe allocated to a UEmay be allocated to a UE or a UE group, based on a D2D SA resource.

Information associated with a D2D data transmission subframe to be usedfrom among D2D data transmission subframes, which are respectively basedon R times-repeated D2D data transmission resource bitmaps, may betransmitted, through the D2D SA resource.

As described above, when the D2D data transmission resource bitmap isrepeated R times, the R times-repeated D2D data transmission resourcebitmaps may be indexed with B₀ to B_(R-1) Information indicating a UE ora UE group for which a D2D data transmission subframe based on each ofthe D2D data transmission resource bitmaps corresponding to B0 to BR−1,is to be used, may be transmitted through the D2D SA resource.

Alternatively, from among R times-repeated D2D data transmissionresource bitmaps, a combination of D2D data transmission resourcebitmaps that may be allocated to a UE or a UE group may be configured,and the configured combination may be used for the UE or the UE group.For example, when the number of UEs or UE groups is 2, a D2D dataresource determined based on └R/2┘ (or ┌R/2┐), which is the number ofrepetitions of a D2D data transmission resource bitmap, may be allocatedto a first UE (or a first UE group). For example, a D2D data resourcedetermined based on └R/2┘ (or ┌R/2┐), which is the remaining number ofrepetitions of a D2D data transmission resource bitmap, may be allocatedto a second UE (or a second UE group).

Information associated with a D2D data transmission subframe to be usedfrom among D2D data transmission subframes that are respectively basedon R times-repeated D2D data transmission resource bitmaps transmittedthrough a D2D SA resource, may be transmitted by being included in aT-RPT indication information transmitted through the D2D SA resource, ormay be transmitted to a UE together with the T-RPT indicationinformation.

A D2D data transmission subframe allocated to a UE group may bedetermined based on various methods.

FIG. 6 is a conceptual diagram illustrating a method of allocating a D2Ddata transmission resource, to a UE or a UE group, according to anexemplary embodiment.

Referring to FIG. 6, an index may be allocated for each unit D2D datatransmission resource that forms a D2D data transmission resourceallocated in a D2D data allocation period. A D2D data transmissionresource may be allocated to a UE group, based on an index associatedwith a unit D2D data transmission resource.

The UE group may be determined based on a UE identifier. The UEidentifier may be allocated to a UE through a D2D SA transmissionresource, and the UE group may be configured based on the UE identifier.To configure N UE groups, a modular N arithmetic may be executed withrespect to the value of a UE identifier. When the result of the modularN arithmetic is 0, it indicates UE group 0. When the result of themodular N arithmetic is 1, it indicates UE group 1. When the result ofthe modular N arithmetic is N−1, it indicates UE group N−1.

When unit D2D data transmission resources are sequentially indexed, atotal of M unit D2D data transmission resources from 0 to M−1 may bedefined. Unit D2D data transmission resources corresponding toeven-numbered indices from among the unit D2D data transmissionresources corresponding to indices from 0 to M−1, may be a D2D datatransmission resource 600 for UE group 0. Alternatively, unit D2D datatransmission resources corresponding to odd-numbered indices from amongthe unit D2D data transmission resources corresponding to indices from 0to M−1, may be a D2D data transmission resource 650 for UE group 1.

As another example, a D2D data transmission resource for each of threeUE groups may be determined by a modular arithmetic. Unit D2D datatransmission resources that have a modular arithmetic result of 0, fromamong the unit D2D data transmission resources corresponding to indicesfrom 0 to M−1, may be a D2D data transmission resource for UE group 0.Unit D2D data transmission resources that have a modular arithmeticresult of 1, from among the unit D2D data transmission resourcescorresponding to indices from 0 to M−1, may be a D2D data transmissionresource for UE group 1. Unit D2D data transmission resources that havea modular arithmetic result of 2, from among the unit D2D datatransmission resources corresponding to indices from 0 to M−1, may be aD2D data transmission resource for UE group 2.

In addition, a D2D data transmission subframe may be allocated to a UEgroup, based on an RRC signaling or a D2D SA transmission resource.

For example, when the number of UE groups is N, ┌log₂ N┐ bits may betransmitted to a UE through an RRC signaling or a D2D SA transmissionresource, as UE group indication information for indicating a UE group.When the number of UE groups is 2, UE group indication information maybe 1 bit. When UE group indication information that a UE receives is 0,a UE group that includes the UE may be UE group 0. Conversely, when UEgroup indication information that a UE receives is 1, a UE group thatincludes the UE may be UE group 1.

As described above, after a UE group is configured for each UE, based onan RRC signaling or a D2D SA transmission resource, a D2D datatransmission resource may be allocated to each UE group. For example,unit D2D data transmission resources corresponding to even-numberedindices from among the unit D2D data transmission resourcescorresponding to indices from 0 to M−1, may be the D2D data transmissionresource 600 for UE group 0. Alternatively, unit D2D data transmissionresources corresponding to odd-numbered indices from among the unit D2Ddata transmission resources corresponding to indices from 0 to M−1, maybe the D2D data transmission resource 650 for UE group 1.

Information associated with a UE group including a UE may be transmittedby being included in T-RPT indication information transmitted through aD2D SA resource, or may be transmitted to a UE together with the T-RPTindication information.

Hereinafter, FIG. 7 and FIG. 8 disclose a method of transmittingcell-specific information and UE-specific information (or UEgroup-specific information).

The cell-specific information may be information associated with a D2Ddata allocation period, information associated with a D2D datatransmission resource offset, information associated with a D2D datatransmission resource bitmap, information associated with the number ofrepetitions of a D2D data transmission resource bitmap, or the like.

The UE-specific information (or UE group-specific information) may beD2D data transmission resource allocation information, which isinformation for allocating a D2D data transmission resource to anindividual UE or a UE group.

FIG. 7 is a conceptual diagram illustrating a method of transmittinginformation for D2D communication according to an exemplary embodiment.

FIG. 7 discloses a method of transmitting cell-specific information forD2D communication.

In the case of first mode communication, cell-specific information forD2D communication may be transmitted through a System Information Block(SIB) 700. For example, the SIB 700 that is transmitted from a BS to aUE in coverage (in-coverage UE) may include cell-specific informationfor D2D communication. Alternatively, the BS may transmit cell-specificinformation for D2D communication to the UE through a higher layersignaling. For example, the BS may transmit cell-specific information toan RRC-connected UE, through an RRC signaling 720.

The cell-specific information for D2D communication, transmitted fromthe BS to a UE through the SIB 700 or the higher layer signaling 720,may be transmitted to another UE through a specific channel 740 for D2Dcommunication (for example, a Physical Device to Device Shared Channel(PD2DSCH)). For example, an in-coverage UE adjacent to the BS maytransfer cell-specific information that is received through the SIB 700or the higher layer signaling 720, to a UE located in an edge of a cell(an edge-of-cell-coverage UE) through the PD2DSCH 740.

As another method, cell-specific information for D2D communication whichis transmitted from the BS to a UE through the SIB 700 or the higherlayer signaling 720, may be transmitted to another UE through a D2D SAresource. For example, a UE adjacent to the BS may transfercell-specific information that is received through the SIB 700 or thehigher layer signaling 720, to a UE located in an edge-of-cell-coverageUE through a D2D SA resource 760. Although the D2D SA resource 760 is aresource specific to a UE, information transmitted through the D2D SAresource 760 may be information common to a plurality of UEs included ina UE group. For example, the SIB 700 or the higher layer signaling 720may include broadcasted SIB information or an RRC signaling configuredfor a predetermined UE.

In the case of second mode communication, cell-specific information forD2D communication may be signaled through a predetermined D2D channel(for example, a PD2DSCH) 780. For example, a UE corresponding to an ISStransmits cell-specific information for D2D communication to a UEoutside coverage (an out-of-coverage UE) through a predetermined D2Dchannel. Alternatively, cell-specific information for D2D communicationmay be transmitted between UEs through a D2D SA resource 790. Althoughthe D2D SA resource 790 is a resource specific to a UE, informationtransmitted through the D2D SA resource 790 may be information common toa plurality of UEs included in a UE group.

FIG. 8 is a conceptual diagram illustrating a method of transmittinginformation for D2D communication according to an exemplary embodiment.

FIG. 8 discloses a method of transmitting UE-specific information or UEgroup-specific information for D2D communication.

The UE-specific information (or UE group-specific information) for D2Dcommunication may be indicated based on a UE identifier. For example, aUE identifier may be allocated to a UE through a D2D SA resource 820 orthe like. UE-specific information (or UE group-specific information) forD2D communication may be determined based on a rule or a numericalformula (for example, a modular arithmetic) defined in advance based ona UE identifier allocated to a UE.

Also, UE-specific information (or UE group-specific information) for D2Dcommunication may be transmitted to a UE, through an RRC signaling 800or a D2D SA communication resource 820.

Cell-specific information for D2D communication and UE-specificinformation for D2D communication may be transmitted to a UE throughvarious signaling methods disclosed in FIGS. 7 and 8.

In the case of cell-specific information for D2D communication, thefollowing various signaling methods may be used for transmission to aUE.

For example, cell-specific information for D2D communication may betransmitted to a UE as a signaling through an SIB. In this instance, anin-coverage UE may receive, from a BS (eNodeB), a signaling associatedwith cell-specific information through an SIB.

As another example, cell-specific information for D2D communication maybe transmitted to a UE as a signaling through an SIB and a PD2DSCH. Inthis instance, an in-coverage UE may receive, from a BS, a signalingassociated with cell-specific information through an SIB. Also, anedge-of-cell-coverage UE may receive, from an in-coverage D2D UE, asignaling associated with cell-specific information through a PD2DSCH.

As another example, cell-specific information for D2D communication maybe transmitted to a UE as a signaling through a PD2DSCH. In thisinstance, an out-of-coverage UE may receive a signaling associated withcell-specific information through a PD2DSCH, from an ISS or anotherout-of-coverage D2D UE.

As another example, cell-specific information for D2D communication maybe transmitted to a UE as a signaling through an SIB and an SA. In thisinstance, an in-coverage D2D UE may receive, from a BS, the signalingthrough the SIB, and the edge-of-cell-coverage D2D UE may receive thesignaling through the SA from the in-coverage D2D UE. Here, thesignaling through the SA is a dedicated signaling which is specific toeach UE, but actually, it may be configured to be common to a pluralityof UEs included in a UE group.

As another example, cell-specific information for D2D communication maybe transmitted to a UE as a signaling through an SA. In this instance,an out-of-coverage D2D UE may receive a signaling associated withcell-specific information through an SA, from an ISS or anotherout-of-coverage D2D UE. Here, the signaling through the SA is adedicated signaling which is specific to each UE, but actually, it maybe configured to be common to a plurality of UEs included in a UE group.

As another example, cell-specific information for D2D communication maybe transmitted to a UE as a higher layer signaling such as an RRC or thelike. In this instance, an RRC-connected D2D UE may receive, from a BS(eNodeB), a signaling associated with cell-specific information throughan RRC. Here, a higher layer signaling such as an RRC or the like is adedicated signaling which is specific to each UE, but actually, it maybe configured to be common to a plurality of UEs included in a UE group.

In the case of UE-specific information for D2D communication, thefollowing various signaling methods may be used for transmission to aUE.

For example, UE-specific information for D2D communication may betransmitted to a UE through a UE identifier. Here, the UE identifier maybe a UE identifier included in an SA. In this instance, a SA receivingD2D UE may receive an SA including the UE identifier from an SAtransmitting D2D UE.

As another example, UE-specific information for D2D communication may betransmitted to a UE as a higher layer signaling such as an RRC or thelike. In this instance, an RRC-connected D2D UE may receive, from a BS(eNodeB), a signaling associated with UE-specific information through anRRC. Here, a higher layer signaling such as an RRC or the like, may beconfigured as a dedicated signaling which is specific to each UE.

As another example, UE-specific information for D2D communication may betransmitted to a UE through an SA. In this instance, an SA receiving D2DUE may receive a signaling associated with UE-specific informationthrough an SA, from an SA transmitting D2D UE. Here, a signaling throughthe SA may be configured as a dedicated signaling which is specific toeach UE.

In the case of transmitting cell-specific information for D2Dcommunication and/or UE-specific information for D2D communication to aUE through a higher layer signaling such as an RRC or the like, adefault value may be indicated as a signaling value for an RRC idle D2DUE. For example, when one of 2 and 3 is indicated, through an RRC, as aD2D data transmission resource offset value for an RRC-connected D2D UE,2 which is a default value may be used as a D2D data transmissionresource offset value for an RRC idle D2D UE.

In the case in which the first mode communication is actually set for aD2D UE and the D2D UE that is set to operate as the first modecommunication needs to utilize a D2D resource pool for second modecommunication (for example, in the case in which a BS configures a D2Dresource pool (D2D reception resource pool) for the first modecommunication, and a D2D resource pool (D2D transmission resource pooland D2D reception resource pool) for the second mode communication isneeded to be indicated for exceptional cases, or the like), when the BSdoes not indicate information associated with the D2D resource pool forthe second mode communication through an SIB, the following methods maybe considered.

First, information associated with both the D2D transmission resourcepool and the D2D reception resource pool of the second modecommunication may be configured in advance through a higher layersignaling such as an RRC or the like. As another method, the D2Dreception resource pool of the second mode communication has aconfiguration identical to that of the D2D reception resource pool ofthe first mode communication, and information associated with the D2Dtransmission resource pool of the second mode communication may beconfigured in advance through a higher layer signaling such as an RRC orthe like. As another method, the D2D reception resource pool of thesecond mode communication may have a configuration identical to that ofthe D2D reception resource pool of the first mode communication, and theD2D transmission resource pool of the second mode communication may havea configuration identical to that of the D2D reception resource pool ofthe second mode communication.

Hereinafter, an example of a combination of various signaling methodsdisclosed in FIGS. 7 and 8 for transmitting cell-specific informationand UE-specific information for D2D communication, will be disclosed.This is merely an example, and it is apparent that other variouscombinations are also possible based on the above described signalingmethods.

(1) First Signaling Method

Cell-specific information for D2D communication may be transmitted to aUE through an SIB or through an SIB and a PD2DSCH. UE-specificinformation (or UE group-specific information) for D2D communication maybe determined based on a UE identifier.

(2) Second Signaling Method

Cell-specific information for D2D communication may be transmitted to aUE through an RRC signaling. UE-specific information (or UEgroup-specific information) for D2D communication may also betransmitted through an RRC signaling.

Hereinafter, operations of a UE that transmits traffic data and a UEthat receives traffic data in D2D communication executed in FDD or TDD,will be described.

FIG. 9 is a conceptual diagram illustrating operations of a first UE anda second UE in FDD, according to an exemplary embodiment.

Referring to FIG. 9, a D2D data transmission resource may be determinedbased on a D2D data transmission resource determining method disclosedin FIGS. 4 to 8. A D2D data reception resource may be determined throughvarious methods. For example, when a first UE and a second UE supportfull-duplex, a D2D data transmission resource and a D2D data receptionresource are identical on time axis, and transmission and reception ofdata may be executed in parallel. As another example, when the first UEand the second UE support half duplex, a D2D data transmission resourceand a D2D data reception resource on time axis may be separatelyconfigured. A UE that supports the half duplex may transmit traffic datathrough a part or the entirety of a D2D data transmission resource, andmay receive traffic data from another UE by monitoring a separate D2Ddata reception resource.

Hereinafter, exemplary embodiments provide descriptions under anassumption that a UE supports half duplex and a D2D data transmissionresource and a D2D data reception resource are separately configured.

When it is assumed that a first UE and a second UE execute D2Dcommunication, a first D2D data transmission resource 900 of the firstUE may be a second D2D data reception resource 940 of the second UE, onthe time axis. That is, the second UE may monitor a resourcecorresponding to the first D2D data transmission resource 900 of thefirst UE as the second D2D data reception resource 940, on the timeaxis. To this end, a UE should be aware of information associated with aD2D data transmission resource of another UE that executes D2Dcommunication. The information associated with the D2D data transmissionresource of the other UE that executes D2D communication may betransmitted to a UE through various methods (for example, a D2D SAresource, an SIB, or the like). The information associated with the D2Ddata transmission resource of the other UE may be D2D data transmissionresource allocation information, which is UE-specific information of theother UE.

When the UE is not aware of the information associated with the D2D datatransmission resource of the other UE that executes D2D communication,the UE may execute monitoring associated with remaining resourcesexcluding the D2D data transmission resource, and may receive trafficdata from the other UE. Hereinafter, descriptions will be provided byassuming that a UE is aware of information associated with a D2D datatransmission resource of another UE that executes D2D communication.

The first D2D data transmission resource 900 of the first UE may bedetermined based on cell-specific information and UE-specificinformation associated with the first UE. The second D2D datatransmission resource 920 of the second UE may be determined based oncell-specific information and UE-specific information associated withthe second UE. The first UE and the second UE may be grouped intopredetermined UE groups based on the UE-specific information associatedwith the first UE and the UE-specific information associated with thesecond UE.

For example, unit D2D data transmission resources corresponding toeven-numbered indices from among the unit D2D data transmissionresources corresponding to indices from 0 to M−1, may be the D2D datatransmission resource 900 for a first UE group including the first UE.For example, unit D2D data transmission resources corresponding toeven-numbered indices from among the unit D2D data transmissionresources corresponding to indices from 0 to M−1, may be the D2D datatransmission resource 920 for a second UE group including the second UE.In this instance, a resource corresponding to the second D2D datatransmission resource 920 on the time axis, may be the first D2D datareception resource 960 of the first UE. Also, a resource correspondingto the first D2D data transmission resource 900 may be the second D2Ddata reception resource 940 of the second UE, on the time axis.

The first UE may transmit traffic data through the first D2D datatransmission resource 900 allocated out of the first D2D datatransmission resource. Also, the first UE monitors the first D2D datareception resource 960 (the second D2D data transmission resource), andmay receive traffic data transmitted from the second UE.

The second UE may transmit traffic data through the second D2D datatransmission resource 900 allocated out of the second D2D datatransmission resource. Also, the second UE monitors the second D2D datareception resource (the first D2D data transmission resource), and mayreceive traffic data transmitted from the first UE.

When a third UE that executes D2D communication with the first UE isadded, the first D2D data reception resource of the first UE mayadditionally include a third D2D data transmission resource of the thirdUE. That is, the first UE may monitor the second D2D data transmissionresource of the second UE and the third D2D data transmission resourceof the third UE, as the D2D data reception resource of the first UE.

FIG. 10 is a conceptual diagram illustrating operations of a first UEand a second UE in TDD, according to an exemplary embodiment.

FIG. 10 assumes that a first UE and a second UE execute TDD-based D2Dcommunication.

In TDD, a D2D data transmission resource may be determined based on aD2D data transmission resource determining method disclosed in FIGS. 4to 8.

It is assumed that information associated with a D2D data transmissionresource of another UE that executes D2D communication is transmitted toa UE through various methods (for example, a D2D SA resource, an SIB, orthe like). In this instance, a resource corresponding to a second D2Ddata transmission resource 1060 may be a first D2D data receptionresource 1020 of the first UE on the time axis, like the above describedcase of FDD. Also, a resource corresponding to the first D2D datatransmission resource 1000 may be the second D2D data reception resource1040 of the second UE, on the time axis.

The first UE may transmit traffic data through a part or the entiretyselected out of the first D2D data transmission resource 1000. Also, thefirst UE monitors the first D2D data reception resource 1020 (the secondD2D data transmission resource), and may receive traffic datatransmitted from the second UE.

The second UE may transmit traffic data through a part or the entiretyselected out of the second D2D data transmission resource 1040. Also,the second UE monitors the second D2D data reception resource 1060 (thefirst D2D data transmission resource), and may receive traffic datatransmitted from the first UE.

When a third UE that executes D2D communication with the first UE isadded, the first D2D data reception resource of the first UE mayadditionally include a third D2D data transmission resource of the thirdUE. That is, the first UE may monitor the second D2D data transmissionresource of the second UE and the third D2D data transmission resourceof the third UE, as the D2D data reception resource of the first UE.

When information associated with a D2D data transmission resource ofanother UE that executes D2D communication based on FDD or TDD is nottransmitted to a UE, the UE may determine a resource excluding the D2Ddata transmission resource as a D2D data reception resource.

FIG. 11 is a flowchart illustrating a traffic data transmittingoperation of a UE according to an exemplary embodiment.

Referring to FIG. 11, a UE determines a D2D data transmission resourcebased on cell-specific information for D2D communication and UE-specificinformation (UE group-specific information) for D2D communication, inoperation S1100.

For example, a UE may receive cell-specific information for D2Dcommunication (for example, information associated with a D2D dataallocation period, information associated with a D2D data transmissionresource offset, information associated with a D2D data transmissionresource bitmap, and information associated with the number ofrepetitions of a D2D data transmission resource bitmap) and UE-specificinformation for D2D communication (for example, D2D data transmissionresource allocation information), through above described variousmethods (an SIB, a PD2DSC, an RRC, a D2D SA resource, or the like). TheD2D data transmission resource may be determined based on a D2D datatransmission resource determining method disclosed in FIGS. 4 to 8.

The UE transmits traffic data based on the determined D2D datatransmission resource in operation S1120.

The UE may transmit traffic data through a part or the entirety of thedetermined D2D data transmission resource.

A UE that fails to obtain synchronization for D2D communication, mayexecute synchronization by taking into consideration informationassociated with a starting point of a D2D data allocation period and/ora location of a current subframe allocated in the D2D data allocationperiod, and may transmit traffic data. For example, a UE that executesinitial access for D2D communication may obtain information associatedwith a starting point of the D2D data allocation period, based on asubframe number of a system frame number (SFN), and may be assigned witha D2D data transmission resource after the starting point of the D2Ddata allocation period.

Alternatively, a UE that executes initial access for D2D communicationmay obtain information associated with a starting point of the D2D dataallocation period, based on a subframe number of a system frame number(SFN), and may be assigned with a D2D data transmission resource after apredetermined point of the D2D data allocation period.

FIG. 12 is a flowchart illustrating a traffic data reception operationof a UE according to an exemplary embodiment.

Referring to FIG. 12, a UE determines a D2D data reception resourcebased on information associated with a D2D data transmission resource ofanother UE that executes D2D communication, in operation S1200.

For example, a UE may receive information associated with a D2D datatransmission resource of another UE, through above described variousmethods (an SIB, a PD2DSC, an RRC, a D2D SA resource, or the like).Cell-specific information between the UE and the other UE are identical,and thus, the UE may receive UE-specific information of the other UE asinformation associated with a D2D data transmission resource of theother.

The UE receives traffic data based on the determined D2D data receptionresource in operation S1220.

The UE may monitor the determined D2D data reception resource, so as toreceive traffic data transmitted from the other UE. In the same manneras the transmission of traffic data, a UE that fails to obtainsynchronization for D2D communication, may execute synchronization bytaking into consideration information associated with a starting pointof a D2D data allocation period and/or a location of a current subframeallocated in the D2D data allocation period, and may transmit trafficdata.

FIG. 13 is a block diagram illustrating a BS and a UE according to anexemplary embodiment.

Referring to FIG. 13, a BS may include a D2D communication resourcedetermining unit 1300, a D2D communication resource informationgenerating unit 1310, a communication unit 1320, and a processor 1330. AUE may include a D2D communication resource determining unit 1350, a D2Dcommunication resource information generating unit 1360, a communicationunit 1370, and a processor 1380. The component elements of the UE andthe BS disclosed in FIG. 13 are configured for illustrative purposes,and a single component element may be embodied as a plurality ofcomponent elements or a plurality of component elements may be embodiedas a single component element.

The component elements of the UE and the BS may be embodied forexecuting the operations of the BS and the UE, which have been describedin FIGS. 4 to 12. For example, the component elements of the BS and theUE may execute the following operations.

A D2D communication resource determining unit 1300 of the BS may beembodied to determine a D2D data transmission resource and a D2D datareception resource of a UE that executes D2D communication. For example,in the case of a first mode communication, the D2D communicationresource determining unit 1300 of the BS may set a D2D data allocationperiod, a D2D data transmission resource offset, a D2D data transmissionresource bitmap, the number of repetitions of a D2D data transmissionresource bitmap to be identical to one another with respect to a UEgroup including a plurality of UEs in a cell, so as to determine a D2Ddata transmission resource for the group of the plurality of UEs.

Also, the D2D communication resource determining unit 1300 may determinea part or the entirety of the D2D data transmission resource as a D2Ddata transmission resource for individual UE included in a UE group orfor each of a plurality of UE groups.

The D2D communication resource information generating unit 1310 of theBS may be embodied to generate the D2D data transmission resource or theD2D data reception resource, which is determined based on the D2Dcommunication resource determining unit 1300. For example, the D2Dcommunication resource information generating unit 1310 of the BS maygenerate information associated with a D2D data transmission resourceoffset, information associated with a D2D data transmission resourcebitmap, and information associated with the number of repetitions of aD2D data transmission resource bitmap, as cell-specific information.Alternatively, the D2D communication resource information generatingunit 1310 of the BS is UE-specific information (or UE group-specificinformation), and may generate a part or the entirety of a D2D datatransmission resource, as D2D data transmission resource allocationinformation associated with a D2D data transmission resource for anindividual UE included in a UE group or for each of a plurality of UEgroups.

The communication unit 1320 of the BS may be embodied to transmit, to anin-coverage UE, cell-specific information and UE-specific information(or UE group-specific information) for D2D communication generated bythe D2D data resource allocation information generating unit 1310.

The processor 1330 of the BS may be embodied to control operations ofthe D2D communication resource determining unit 1300, the D2Dcommunication resource information generating unit 1310, and thecommunication unit 1320.

The D2D communication resource determining unit 1350 of the UE may setand determine a D2D data allocation period, a D2D data transmissionresource offset, a D2D data transmission resource bitmap, the number ofrepetitions of a D2D data transmission resource bitmap to be identicalto one another, with respect to a UE group including a plurality of UEsdetermined based on an ISS, so as to determine a D2D data transmissionresource for the group of the plurality of UEs. Also, the D2Dcommunication resource determining unit 1350 may determine a part or theentirety of the D2D data transmission resource as a D2D datatransmission resource for individual UE included in a UE group or foreach of a plurality of UE groups.

The D2D communication resource determining unit 1350 may set differentD2D data transmission resource offset values for individual UEs includedin a UE group or a plurality of UE groups.

The D2D communication resource information generating unit 1360 of theUE may be embodied to generate information associated with the D2D datatransmission resource or the D2D data reception resource, which isdetermined based on the D2D communication resource determining unit1350. For example when the UE is an ISS in the second modecommunication, the UE may generate cell-specific information andUE-specific information (or UE group-specific information) to betransmitted to another UE.

When the UE is an ISS, the D2D communication resource determining unit1350 of the UE and the D2D communication resource information generatingunit 1360 of the UE may operate. Alternatively, the D2D communicationresource determining unit 1350 of the UE may operate to transmitinformation associated with a D2D data reception resource to bemonitored by another UE.

The communication unit 1370 of the UE may be embodied to transmit, to aUE, cell-specific information and UE-specific information (or UEgroup-specific information) for D2D communication generated by the D2Dcommunication resource information generating unit 1360. Alternatively,when the UE is not an ISS, the communication unit 1370 may be embodiedto receive generated cell-specific information and UE-specificinformation (or UE group-specific information) for D2D communication,from another UE or the BS. Alternatively, the communication unit 1370may be embodied to transmit, to another UE that executes D2Dcommunication, information associated with a D2D data reception resourceto be monitored.

The processor 1380 of the UE may be embodied to control operations ofthe D2D communication resource determining unit 1350 of the UE, the D2Dcommunication resource information generating unit 1360 of the UE, andthe communication unit 1370 of the UE.

According to an exemplary embodiment, the D2D communication resourcedetermining unit 1350 and the D2D communication resource informationgenerating unit 1360 may be configured in one or more processors, e.g.,the processor 1380. The communication unit 1370 may be or the UEseparately include a wireless transceiver.

The wireless transceiver may receive configuration informationassociated with a D2D data transmission resource, the configurationinformation including information of a D2D data allocation period andbeing transmitted from an evolved NodeB (eNB). One or more processors inassociation with one or more memories, e.g., the processor 1380, the D2Dcommunication resource determining unit 1350, and the D2D communicationresource information generating unit 1360, may determine a D2D datatransmission resource offset and a period associated with a D2D datatransmission resource bitmap in each D2D data allocation period, the D2Ddata transmission resource bitmap including at least one bitcorresponding to bit value “1”. The one or more processors may furtherdetermine a pool of subframes corresponding to the bit value “1” of theD2D data transmission resource bitmap, the period associated with theD2D data transmission resource bitmap including the pool of subframes,the pool of subframes corresponding to D2D data transmission resourcesthrough which a D2D data transmission is capable.

The wireless transceiver may be configured to receive information of theD2D data transmission resource offset and information of the D2D datatransmission resource bitmap transmitted from the eNB. Referring to FIG.4, a start point of the period associated with the D2D data transmissionresource bitmap may be determined based on a start point of each D2Ddata allocation period and the D2D data transmission resource offset. Aplurality of repetitions of the D2D data transmission resource bitmapmay correspond to uplink subframes in the period associated with the D2Ddata transmission resource bitmap.

Further, a plurality of repetitions of the D2D data transmissionresource bitmap may be associated with the period associated with theD2D data transmission resource bitmap as shown in e.g., FIG. 4. The poolof subframes corresponding to the bit value “1” of the D2D datatransmission resource bitmap may have a repetitive pattern in the periodassociated with the D2D data transmission resource bitmap in accordancewith the plurality of repetitions of the D2D data transmission resourcebitmap. The D2D data transmission resource offset indicated as a numberof subframes.

According to an exemplary embodiment, the communication unit 1370 mayreceive configuration information associated with a D2D datatransmission resource, the configuration information includinginformation of a D2D data allocation period, information of a D2D datatransmission resource offset, and information of a D2D data transmissionresource bitmap. The one or more processors may determine a D2D datatransmission resource in the D2D data allocation period among uplinksubframes configured based on a radio frame structure of a FrequencyDivision Duplexing (FDD) scheme or a Time Division Duplexing (TDD)scheme, each radio frame according to the radio frame structureincluding 10 subframes. The one or more processors may determine, withinthe D2D data allocation period, a plurality of repetitions of a D2D datatransmission resource bitmap based on the D2D data transmission resourceoffset. In an example, the one or more processors may determine uplinksubframes in a period associated with the D2D data transmission resourcebitmap, the period associated with the D2D data transmission resourcebitmap being preceded by the D2D data transmission resource offset andincluded in the D2D data allocation period. Then, the one or moreprocessors may associate (or map) the D2D data transmission resourcebitmap with the uplink subframes in the period associated with the D2Ddata transmission resource bitmap, the D2D data transmission resourcebitmap including at least one bit corresponding to bit value “1”, eachbit of the D2D data transmission resource bitmap being associated withone of the uplink subframes in the period associated with the D2D datatransmission resource bitmap. The one or more processors may determine apool of uplink subframes corresponding to the bit value “1” of the D2Ddata transmission resource bitmap and located in the period associatedwith the D2D data transmission resource bitmap, the pool of uplinksubframes corresponding to D2D data transmission resources through whicha D2D data transmission is capable.

The uplink subframes in the period associated with the D2D datatransmission resource bitmap may be arranged in an ascending order ofthe radio frame structure, and the D2D data transmission resource bitmapmay be associated with the arranged uplink subframes in the periodassociated with the D2D data transmission resource bitmap in an orderfrom the most significant bit to the least significant bit. Referring toFIG. 4, after associating the least significant bit, the D2D datatransmission resource bitmap is repeated in the association with thearranged uplink subframes in the order from the most significant bit tothe least significant bit. A start point of the period associated withthe D2D data transmission resource bitmap may be determined based on astart point of the D2D data allocation period and the data transmissionresource offset. The data transmission resource offset may correspond toan offset between the start point of the D2D data allocation period andthe start point of the period associated with the D2D data transmissionresource bitmap. A plurality of D2D data allocation periods eachincludes the data transmission resource offset and the period associatedwith the D2D data transmission resource bitmap.

The processors may include an application-specific integrated circuit(ASIC), another chipset, a logic circuit, and/or a data processingdevice. The memories may include a Read-Only Memory (ROM), a RandomAccess Memory (RAM), a flash memory, a memory card, a storage mediumand/or another storage device. The RF units may include a basebandcircuit for processing a wireless signal. When an embodiment is embodiedas software, the described scheme may be embodied as a module (process,function, or the like) that executes the described function. The modulemay be stored in a memory, and may be executed by a processor. Thememory may be disposed inside or outside the processor, and may beconnected to the processor through various well-known means.

In the described exemplary system, although methods are described basedon a flowchart as a series of steps or blocks, aspects of the presentinvention are not limited to the sequence of the steps and a step may beexecuted in a different order or may be executed in parallel withanother step. In addition, it is apparent to those skilled in the artthat the steps in the flowchart are not exclusive, and another step maybe included or one or more steps of the flowchart may be omitted withoutaffecting the scope of the present invention.

What is claimed is:
 1. A method comprising: receiving, by a userequipment (UE) and from an evolved NodeB (eNB), configurationinformation associated with a device-to-device (D2D) data transmissionresource, the configuration information comprising information of a D2Ddata allocation period; determining, in each D2D data allocation period,a D2D data transmission resource offset and a duration associated with aD2D data transmission resource bitmap, the D2D data transmissionresource bitmap comprising at least one bit having bit value 1 and atleast one bit having bit value 0; determining, based on a length of theduration and based on a length of the D2D data transmission resourcebitmap, a quantity of repetition of the D2D data transmission resourcebitmap; and determining, based on the repetition of the D2D datatransmission resource bitmap, a pool of subframes in the durationassociated with the D2D data transmission resource bitmap, the pool ofsubframes corresponding to D2D data transmission resources, wherein thepool of subframes is associated with the bit value 1 of the D2D datatransmission resource bitmap and has a repetitive pattern in theduration associated with the D2D data transmission resource bitmap. 2.The method of claim 1, further comprising: receiving, by the UE and fromthe eNB, information of the D2D data transmission resource offset andinformation of the D2D data transmission resource bitmap.
 3. The methodof claim 1, wherein: a start point of the duration associated with theD2D data transmission resource bitmap is determined based on a startpoint of each D2D data allocation period and the D2D data transmissionresource offset.
 4. The method of claim 1, wherein: the repetition ofthe D2D data transmission resource bitmap is associated with uplinksubframes in the duration associated with the D2D data transmissionresource bitmap.
 5. The method of claim 1, wherein: the D2D datatransmission resource offset is indicated as a quantity of subframes. 6.The method of claim 1, wherein: the D2D data allocation period isrepeated a plurality of times in a time axis; and in each D2D dataallocation period, the D2D data transmission resource offset precedesthe duration associated with a D2D data transmission resource bitmap. 7.A user equipment (UE) comprising: a wireless transceiver configured to:receive, from an evolved NodeB (eNB), configuration informationassociated with a device-to-device (D2D) data transmission resource, theconfiguration information comprising information of a D2D dataallocation period; and one or more processors configured to: determine,in each D2D data allocation period, a D2D data transmission resourceoffset and a duration associated with a D2D data transmission resourcebitmap, the D2D data transmission resource bitmap comprising at leastone bit having bit value 1 and at least one bit having bit value 0; anddetermine, based on a length of the duration and based on a length ofthe D2D data transmission resource bitmap, a quantity of repetition ofthe D2D data transmission resource bitmap, determine, based on therepetition of the D2D data transmission resource bitmap, a pool ofsubframes in the duration associated with the D2D data transmissionresource bitmap, the pool of subframes corresponding to D2D datatransmission resources, wherein the pool of subframes is associated withthe bit value 1 of the D2D data transmission resource bitmap and has arepetitive pattern in the duration associated with the D2D datatransmission resource bitmap.
 8. The UE of claim 7, wherein the wirelesstransceiver is configured to receive, from the eNB, information of theD2D data transmission resource offset and information of the D2D datatransmission resource bitmap.
 9. The UE of claim 7, wherein: a startpoint of the duration associated with the D2D data transmission resourcebitmap is determined based on a start point of each D2D data allocationperiod and the D2D data transmission resource offset.
 10. The UE ofclaim 7, wherein: the repetition of the D2D data transmission resourcebitmap is associated with uplink subframes in the duration associatedwith the D2D data transmission resource bitmap.
 11. The UE of claim 7,wherein: the D2D data transmission resource offset is indicated as aquantity of subframes.
 12. The UE of claim 7, wherein: the D2D dataallocation period is repeated a plurality of times in a time axis; andin each D2D data allocation period, the D2D data transmission resourceoffset precedes the duration associated with a D2D data transmissionresource bitmap.
 13. A method comprising: receiving, by a user equipment(UE) and from an evolved NodeB (eNB), configuration informationassociated with a device-to-device (D2D) data transmission resource, theconfiguration information comprising information of a D2D dataallocation period; determining, in each D2D data allocation period, aD2D data transmission resource offset and a duration associated with aD2D data transmission resource bitmap, the D2D data transmissionresource bitmap comprising at least one bit having bit value 1;determining, based on a length of the duration and based on a length ofthe D2D data transmission resource bitmap, a quantity of repetition ofthe D2D data transmission resource bitmap; and determining, based on therepetition of the D2D data transmission resource bitmap, a pool ofsubframes associated with the bit value 1 of the D2D data transmissionresource bitmap, the duration associated with the D2D data transmissionresource bitmap comprising the pool of subframes, and the pool ofsubframes corresponding to D2D data transmission resources, wherein theD2D data transmission resource offset is indicated as a quantity ofsubframes.
 14. The method of claim 13, further comprising: receiving, bythe UE and from the eNB, information of the D2D data transmissionresource offset and information of the D2D data transmission resourcebitmap.
 15. The method of claim 13, wherein: a start point of theduration associated with the D2D data transmission resource bitmap isdetermined based on a start point of each D2D data allocation period andthe D2D data transmission resource offset.
 16. The method of claim 13,wherein: the repetition of the D2D data transmission resource bitmap isassociated with uplink subframes in the duration associated with the D2Ddata transmission resource bitmap.
 17. The method of claim 13, wherein:the pool of subframes is associated with the bit value 1 of the D2D datatransmission resource bitmap and has a repetitive pattern in theduration associated with the D2D data transmission resource bitmap. 18.The method of claim 13, wherein: the D2D data allocation period isrepeated a plurality of times in a time axis; and in each D2D dataallocation period, the D2D data transmission resource offset precedesthe duration associated with a D2D data transmission resource bitmap.